Aerodynamics

Any glider pilot’s whish

Very good climbing characteristics, an excellent glide ratio - even at high speeds, optimal thermalling performance, and all in all very pleasant handling characteristics. The dream could be realized with Antares. Its aerodynamic layout is the result of an ambitious research project which took a number of years. We have exploited all conceivable possibilities to optimize our glider.

Wing geometry

While laying out the aerodynamic design for the Antares 20E the Antares 18T was already part of our plan. When designing the Antares series, it was an immense extra challenge to realize an optimized 20 meter geometry while at the same time keeping an eye on the optimization of the 18 meter layout. We managed an almost unbelievable work of art. For the sake of a preferably low induced drag we materialized super-elliptical designs on both wingspan versions.

The secret of this trick is the inner wing’s geometry. The wing includes an about two meter long rectangular inner section, which may be shortened (or lengthened) without any negative consequences. For the Antares 18T we simply reduced the length these wing sections by one meter on each side. Another advantage of this solution is that - except for a variably configured inner part - our wing molds can be used for both Antares versions.

The result of this layout optimization is a wing geometry with an induced drag which is only 0,1 % higher than the value of an untwisted elliptic wing - the shape which identifies the theoretic optimum. Among other features, the combination of an enlarged depth at the outer wings and the winglets are responsible for the glider’s good natured flight characteristics. The winglets have been designed together with the wings; so they form an aerodynamic entity which permitted us to reduce the induced drag by another 5 %. The induced drag of an Antares 18T wing therefore measures just 95 % of an untwisted elliptic wing with the same wingspan.

High wing loading

In order to achieve maximal performance in all conditions, the Antares 18T offers its pilot an extremely wide range of possible wing loading configurations. With a minimum wing loading of 31,9 kg/m² you may take advantage of the weakest thermals even on barely flyable days. The Antares 18T’s urge to go at its maximum take-off weight of 660 kg (G/Smax = 60,2 kg/m²) simply causes ecstasy. Flights with the Antares 18T and the experience gained from Antares 20E have proven that an Antares 18T also at its maximum wing loading is still very sensitive to thermals. It’ll let the pilot know immediately where to go, and he will be able to even use ripped updrafts.

The wings of the Antares 18T are equipped with 6 integral tanks, providing a total capacity of 208 liters (55 US gal.). This gigantic tank capacity was achieved because the inner part of the wing spar is positioned noticeably toward the back of the wing compared to common designs. To compensate for a c.g. displacement due to water ballast, the Antares 18T is equipped with an additional tank, which is divided into two compartments, in the vertical stabilizer. It contains approximately 6 liters (1,6 US gal.). Altogether, the glider offers a total tank volume of 214 liters (56.6 US gal.).

The tank system is entirely laid out as a three level design. Its grading is 214 liters , 170 liters and 110 liters. When dumping the water, the ballast tank in the tail will automatically be emptied corresponding to the water loss in the wings. The wing loading may thus be adapted without negatively affecting the position of the center of gravity. The result is a perfect c.g. in all load conditions.

Fast glide

The Antares families’ aerodynamic has been configured to reach high gliding speeds. So our Antares 18S/T has its best glide ratio between 100 km/h (54 knots) and 135 km/h (73 knots). In general we recommend carrying water ballast, because with the optimization for fast soaring the pilot of an Antares 18T with a high wing loading can take advantage of the excellent gliding characteristics in most cross country situations.

Handling

The Antares 18T is thanks to its full span flaperons incredibly well maneuverable. The flap regulation is based on a noel control system. Additionally we could significantly reduce friction resistance in the entire control system by consequently using high quality ball bearings instead of slide bearings. The result is extraordinarily smooth controls.

Big control surfaces with high aspect ratios and state-of-the-art airfoils guarantee for perfect controls under any circumstance in flight and in any wing loading configuration. Meanwhile these control surfaces produce minimal drag.

Highly extendable three-stage Schempp-Hirth air brakes make the landing procedure safe. Even at steep angles the glider does not loose much buoyancy. So the stall speed is only a little bit higher with extended brakes.

All these factors make the Antares 18T a smoothly maneuverable and most agile sailplane. Yet it does not seem “nervous”. Our Antares 18T flies stable; it reacts very well and tells you about thermal activities in the air. Its maneuverability is comparable to a 15 meter glider.